Dentures and other removable orthodontic appliances have in the past been cleansed by brushing. In more recent years various cleansing compositions have been developed to permit thorough and convenient cleansing of such orthodontic appliances by soaking in a solution of the cleansing composition. These products have been improved by adding to the formulations, in tablet or granular form, various compounds to cause effervescence in the cleansing solution. This effervescence aids in dispersing the formulation both by generating a "stirring" action and by "exploding" the tablet or granule as a result of internal gas generation within the tablet or granule. See for example, U.S. Pat. No. 2,931,776 which teaches the use of an anhydrous perborate in a denture cleanser to cause effervescence. The sodium perborate releases oxygen which in addition to causing effervescence contributes, to a minor extent, to the bleaching of the orthodontic appliance.
Potassium monopersulfate has been used as a bleaching agent for dentures. U.S. Pat. No. 3,243,377 discloses a composition containing either anhydrous sodium perborate or potassium monopersulfate in conjunction with an organic acid and a cleansing completion indicator.
U.S. Pat. No. 4,405,486 discloses a method for stabilizing the perborate salts by mixing the perborate with a polymeric fluorocarbon, compressing the mixture and then granulating the composition for use in denture cleaning compositions. As used in the specification and claims the term "denture" means all those removable orthodontic appliances such as false teeth, dental plates and bridges.
In an effort to improve the effectiveness of denture cleansing compositions U.S. Pat. No. 3,936,385 discloses the use of a chlorine generating compound such as dichloroisocyanurates. Although these chlorine generating compositions are effective cleansing agents they are not well accepted because of the chlorine odor.
Chlorine free bleaches which rely on the generation of active oxygen have long been known in the art for use in laundry detergents. These compounds use perborates and persulfates as the oxygen containing compounds of the composition.
British Pat. No. 886,188, discloses certain peroxy acids for use in laundry detergents. In particular, substituted perbenzoic acids, such as chloroperoxybenzoic acid are said to have improved stability over other peracids. British Pat. No. 1,269,677, discloses a synergistic bleaching effect when monopersulfates are used in conjunction with organic peroxy acids. Such monopersulfates are believed to consist essentially of the triple salt KHSO.sub.5 KHSO.sub.4 K.sub.2 SO.sub.4 KHSO.sub.4 K.sub.2 SO.sub.4 and 2KHSO.sub.5. In the mole ratio of about 2:1:1 the foregoing triple salt is known commercially as OXONE.RTM. and sold by E. I. duPont De Nemours & Co. Inc.
U.S. Pat. No. 3,773,673 teaches similar laundry detergent compositions wherein the ratio of monopersulfate to organic peroxy compound is about 1:1 to 1:3. A preferred pH range for effective use of the persulfate/peracid combination of 8.5-11 is disclosed. The preferred organic peroxy compounds are the substituted perbenzoic acids, e.g., p-methoxyperbenzoic acid, and their alkali metal or ammonium salts.
The organic peroxy acids, however, are generally unstable and various methods have been used to improve their stability. The aforementioned British Pat. No. 1,269,677 discloses a stabilizing method which consists of blending the organic peroxy acid with inert compounds to minimize the contact between the peroxy acids and other compounds of the composition, the inert compound being removed by solution, melting or abrasion in the washing process. U.S. Pat. No. 4,126,573, discloses peroxy acids coated with surfactants useful in bleaching fabrics.
Other combinations of organic peroxy acids for use in laundry detergents are disclosed in an EPC application published Jan. 6, 1983 under publication number 0 068 547. A combination of a hydrophilic organic peroxy acid and a hydrophobic peroxy acid are disclosed to have improved effectiveness in laundry bleaches. U.S. Pat. No. 4,126,573 discloses peroxy acids coated with surfactants.
U.S. Pat. No. 4,325,828 discloses a laundry bleach composition which comprises an organic peroxy acid in combination with a perborate salt as the bleaching agent.
There have been no disclosures of which this inventor is aware, of the use of organic peroxy acids in denture cleansing compositions. A primary reason is that the most economical and stable organic peroxy acids which have been available are the substituted perbenzoic acids, and these compounds are not sufficiently stable to be used in denture cleansing composition.